One implementation of Automatic Protection Switching (APS) includes using a “protect” POS (Packet Over Synchronous Optical Network/Synchronous Digital HierarchyPacket Over) interface in a SONET (Synchronous Optical Networking) network as a backup for a “working” POS interface. When the working interface fails, the backup POS interface quickly assumes the failing interface's traffic load.
According to a conventional primary/backup configuration, the two circuits can be terminated in the same router, or in different routers. For example, a first router (e.g., router A) can be configured with a “working” interface. A second router (e.g., router B) can be configured with the “protect” (e.g., backup) interface. If the working interface on router A becomes unavailable, the connection automatically switches over to the protect interface on router B. Conventional techniques enable implementing APS, as discussed above, using network layer 2 interfaces in respective routers.